GOSR2 and progressive myoclonus epilepsy: We show that the milder course of disease in a compound heterozygous PME patient for GOSR2 p.Gly144Trp and p.Lys164del, when compared to patients homozygous for GOSR2 p.Gly144Trp, is due to less severe impairment of SNARE function by the p.Lys164del mutations.